Forgot to add reference in Personal Statement, but in-text citation is present

[SeaRupee]

I know, I know, this does not reflect well on me at all as a graduate student. I have no excuse; I was at my computer for sixteen hours and after reading my personal statement a thousand times, I missed it. The citation was not for data or results, just a research technique I employed in my undergrad research. I added the correct in-text citation and promptly forgot to add it in the references. I'm terrified. I desperately need to get into that graduate school. Is my mistake going to put my application in the paper shredder? How screwed am I?

P.S. My potential supervisor has already approved me to join his lab, if that means anything.